Field
Embodiments of the invention relate to a method and apparatus for inspecting thin films and multidimensional structures. More particularly, the disclosures relate to a method and apparatus for integrating metrology tools in a multi-chamber vacuum processing system and the like.
Background of the Related Art
The fabrication of microelectronics devices typically involves a complicated process sequence requiring hundreds of individual steps performed on semiconductive, dielectric and conductive substrates. Examples of these process steps include oxidation, diffusion, ion implantation, thin film deposition, cleaning, etching and lithography. As one of leading technologies, NAND scaling is driving fast transition from planar 2D to 3D devices. However, the 3D NAND technology is now encountering new challenges, such as process control, inspection and metrology. Among others, gate stack integrity is as critical as wafer quality. The immediate challenge is how to effectively and accurately measure the thickness (& critical dimensions), roughness, stress, density and defects of complex stacks & structures, such as gate multilayer complex oxide-nitride-oxide (ONO) or oxide-poly-oxide (OPO) stacks of up to a few hundred pairs.
With ever-decreasing device dimensions, the control of critical dimensions and process uniformity becomes increasingly more important. Complex multilayer stacks require precise process monitoring the critical dimensions for the thickness, roughness, stress, density, and potential defects. The critical dimensions are verified by measuring the dimensions with a metrology tool. Conventional tools using transmission electron microscopes (TEM) or scanning electron microscopes (SEM) imaging utilize destructive testing techniques, and are costly and time-consuming, making the conventional tools incapable of automation or in-line integration. Current non-destructive metrology tools in production fabs, including broadband spectroscopic ellipsometry technology among other tools such as x-ray technology tools. The purpose of the metrology tool is to provide and identify anomalies in the substrates during processing. However, the metrology tools currently do not have the throughput with acceptable accuracy, for example, the current throughput has an image classification accuracy of about 80%. The throughput accuracy slows production and potentially allows substrates out of specification to continue processing costing time and money.
Therefore, there is an ongoing need for improved metrology tool performance.